Skenea. mollusca. pectinibranchia. sis 
2. D. nodosa. — Upper side with a nearly central ridge ; under side with a 
row of rather large nodular projections ; aperture nearly round. — Euompha- 
lus nodosus, Sower. Min. Conch, t. xlvi Carboniferous Limestone.^ Derby- 
shire. 
3. D. discors — Whorls three or four, above subimbricated, with four spiral 
projections ; beneath concave, smooth — Euomphalus dis. Sower. Min. Conch, 
t. lii. f. 1 — Carboniferous Limestone., Colebrook Dale. 
4. D. rugosa. — Above imbricated, with four spiral projections; beneath 
plaited ; margin rather acute. — ParTc. Or. Rem. iii. 77- t. vi. f. 7, 8 — Euom- 
phalus rug. Sower. Min. Conch, t. lii. f. 2 — Carboniferous Limestone^ Cole- 
brook Dale. 
5. D. angulosa — Above subimbricated, with three spiral projections ; be- 
neath striated, with five obscurely plaited spiral projections ; aperture ob- 
scurely octangular — Euomphalus ang. Sower. Min. Conch, t. lii. f. 3 — Car- 
boniferous Limestone., Benthall Edge. 
6. D. tuberculata — Discoid, whorls striated spirally and transversely^, with 
a row of transverse tubercles on each side.~In Carboniferous Limestone, West 
Lothian. 
Gen. CIRUS. — -Spire produced. 
1. Leachii. — Longitudinally striated ; whorls many, with several rows of 
tubercles crossed by numerous small ridges ; upper row of tubercles spiri- 
form, compressed. — Sower. Min. Conch, t. ccxix. f. 3 — Under Oolite, Dundry. 
2. nodosus. — Conical, acuminated, or discoid, with an acuminated spiral 
umbo ; spire reversed ; whorls many, with two rows of longitudinally ex- 
tended tubercles, crossed by numerous small ridges. — Sower. Min. Conch, 
(cast) t. cxli. f. 2. and t. ccxix. f. 1, 2, 3 Under Oolite, Dundry. 
Gen. LV. SKENEA. — Spire depressed, and destitute of 
spinous processes. 
264. S. depressa. — Whorls three or four, wrinkled across, 
with a deep groove for the separating line. 
Serpula cornea, Adams, Linn. Trans, v. v. t. i. f. 33. — Helix depressa, 
Mont. Test. Brit. 439, t. xiii. f. 5. — At the roots of fuci, common. 
Breadth one line ; colour brown ; whorls round ; beneath, a large central 
cavity exposing the upper volutions ; above, the whorls are nearly on a level, 
their central edge bending suddenly at the separating line, and forming a 
deep groove ; the transverse lines of growth are irregular and rough ; aper- 
ture circular, detached from the body-whorl, sometimes slightly reflected. 
265. S. serpuloides. — Whorls three, white, smooth, and 
glossy. 
Helix utrinque umbillcata apertura rotunda unicianfractus, Walk. Test- 
Min. 7- t. i. f. 26. (the fry). — Helix serp. Mont. Test. Brit. Sup. 147* 
t. xxi. f. 3 — Not uncommon from deep water. 
Breadth about \ ^th of an inch ; subopake ; whorls round, nearly on a level 
above, with a deep separating line ; beneath, with a central cavity, round 
which there are traces, under a high magnifier, of diverging lines of growth ; 
aperture circular, with the margin a little reflected. 
